Electronics > Repair
What more i can do?
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Harry_22:

--- Quote from: fzabkar on December 06, 2024, 10:22:02 pm ---The slow EPROM would at some time be unpacked into RAM, especially when MS-DOS boots. That necessitates remapping the address lines by the chipset. Perhaps you are seeing the result of remapping?

--- End quote ---

May be. Then remapping must be done by Tornado-T chip.
But what is the point of placing EPROM between the 80486DX2 and the Tornado-T?
I would place Tornado-T close to CPU.


--- Quote from: asis on December 07, 2024, 09:20:03 am ---And, the programmer that I recommended to you (Advantech LabTool 48) allows you to do final verification of the EPROM contents, using a check when increasing and decreasing the power supply from the nominal value.
As it turned out, - a very effective verification method that identifies vulnerable UV ROM cells.

I would like to offer you a method that involves supplying additional power to the PCB in the +5V circuit with an acceptable excess of +5.5V, in parallel with the already present - from the standard PSU.


--- End quote ---

We need to work out your version with undervoltage.
It is clearly seen from old traces that unworking machine has a bit lower power supply. Please see the attached picture).

@222Lab_Test222,
please draw us a wiring diagram for LT1085 and the trimmer. What voltages are coming to the board CN10?

PS
Unfortunately you have attached data only from High EPROM. I confused them with Low ones and was already glad that I had found the reason.
Could you attach them as well as missed D3 for working board.
drhex:
And maybe establish if address lines are remapped or on the bus.
222Lab_Test222:

--- Quote from: Harry_22 on December 07, 2024, 12:05:40 pm ---
Could you attach them as well as missed D3 for working board.

--- End quote ---

222Lab_Test222:

--- Quote from: Harry_22 on December 07, 2024, 12:05:40 pm ---
Unfortunately you have attached data only from High EPROM. I confused them with Low ones and was already glad that I had found the reason.


--- End quote ---

Here,

222Lab_Test222:

--- Quote from: Harry_22 on December 07, 2024, 12:05:40 pm ---
What voltages are coming to the board CN10?


--- End quote ---
Here
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